1. Field of the Invention
The present invention relates to a method for forming solder bumps on an integrated circuit die.
2. Background Information
Integrated circuits are typically assembled into a package that is mounted to a printed circuit board. There are various types of integrated circuit packages, including quad flat pack (QFP), organic pin grid array (OLGA), ball grid array (BGA) and controlled collapsed chip connection (C4) packages. C4 packages include a plurality of solder bumps that are attached to an integrated circuit die. The solder bumps are placed onto a package substrate and reflowed to attach the integrated circuit to the substrate.
The solder bumps are typically formed onto the integrated circuit when the circuit is part of a wafer. After solder bump formation the wafer is cut into a plurality of individual dies. Each die is then subsequently mounted to a substrate.
The wafer may be cut by a saw. A stream of highly pressurized water is typically directed at the cut location to cool and lubricate the saw. It has been found that the pressurized water may remove particles of solder from the solder joints during the wafer sawing process. The particles may create electrical shorts when the die is subsequently soldered to the substrate. Additionally, the water may form lead hydroxide on the solder bumps. The lead hydroxide may reduce the integrity of the resultant solder joints formed during the subsequent reflow process of the solder bumps. It would be desirable provide a process which would reduce the amount of contaminants and lead hydroxide formed during the wafer cutting process of a "C4" wafer.